1. Field of the Invention
The present invention relates to a fluorescent device which emits light emitted by irradiating a fluorescent material with excitation light, a lighting apparatus which outputs irradiation light in various colors by using the fluorescent device, and a projector apparatus which uses and projects the irradiation light output from the irradiation apparatus, as a color image.
2. Description of the Related Art
A light source apparatus employs a light emitter which is irradiated with excitation light output from a light source and thereby emits light having a different wavelength from the excitation light. The light source apparatus is used as a light source in various applications; for example, in a lighting apparatus and an image display apparatus.
Such light source apparatuses as mentioned above generally use a light emitting diode (LED) and a laser diode (LD) as light sources, e.g., as semiconductor light sources in many cases. For example, transparent silicone or epoxy resin is used as a resinous binder. A plurality of fluorescent materials are scattered in the resinous binder and form a light emission layer.
The resinous binder is damaged when deterioration is high or particularly intensity of excitation light is high due to excitation light from a semiconductor light source. Further, silicone or a resin such as epoxy resin with scattered fluorescent materials has a low heat conductivity and therefore increases the temperature of the fluorescent materials. The increase in temperature results in shifting of a light emission wavelength of light emitted from the fluorescent materials or a phenomenon of temperature quenching in which light emission intensity lowers. Therefore, luminosity of the light source apparatus deteriorates. For example, substitute materials for the transparent silicone or epoxy resin of the resinous binder are disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2003-258308, Jpn. Pat. Appln. KOKAI Publication No. 2006-282447, and Jpn. Pat. Appln. KOKAI Publication No. 2010-024278. Jpn. Pat. Appln, KOKAI Publication No. 2003-258308 discloses use of a light-transmissible inorganic material, such as glass. Jpn. Pat. Appln. KOKAI Publication No. 2006-282447 and Jpn. Pat. Appln. KOKAI Publication No. 2010-024278 each disclose use of ceramics having a high heat conductivity.
A light emission layer of the fluorescent material formed by using the aforementioned binder (light-transmissible ceramic binder) using ceramics having light-transmissibility is often used as a substitute for a light emission layer using fluorescent materials formed by using the aforementioned resinous binder. Therefore, the light emission layer of the fluorescent materials does not have a structure capable of preventing shifting of a light emission wavelength of light emitted from the fluorescent materials or deterioration of light emission intensity which is caused by temperature increase.